Episode one 'Life from Light' opens with a glimpse of the most spectacular sequence in the series - exploring the Han Son Doong caves of Vietnam (the complete sequence will feature in episode two). Three kilometers inside the cave system Iain discovers a lost rainforest that has grown where the roof has collapsed. Nothing could show more vividly the capacity for plants to colonise barren rock - just as they did when they first ventured on to land. "This rainforest exists because of one thing above all, something which has enabled plants to colonise almost everywhere on earth - light."

The sun is a key character in this film and it stylishly appears throughout in the guise of lens-flares and solar timelapses. It's the perfect symbol of all life on Earth - a star 150 million kms away.

"Plants have this truly remarkable ability to harness energy from out of space, to produce food, it's this ability to eat the sun, to manufacture life from light, that's allowed plants to dominate the planet. This is the most important natural process on earth. It's how the plant kingdom has transformed a lifeless planet into a living world."

Han Son Doong - a rainforest in a cave (Photo: Carsten Peter)

Han Son Doong - a rainforest in a cave (Photo: Carsten Peter)

Han Son Doong - a rainforest in a cave (Photo: Carsten Peter)

Beautifully produced

Like all of Iain's series (though I may be a little biased as I did work on How Earth Made Us), this is well produced, beautifully shot and effortlessly presented. Iain takes us on a thrilling adventure around the world, from South East Asia to the United States, Canada, Australia, South Africa and of course, his native land of Scotland. Complex concepts are made a real pleasure to grasp as Iain demonstrates them using eye-opening experiments, new scientific techniques, and superb graphics - including the best explanation for photosynthesis that I've ever seen on TV.

Although Professor Stewart is mostly known to academia as a seismologist (specialising in earthquakes), he embraces the subject of plants whole-heartedly. His real passion is how the Earth has evolved and changed over millennia, and what could have been more significant than the evolution of photosynthesis. You might say that Iain even puts his lungs into this series - spending two days locked in an airtight chamber full of plants to show the rate at which photosynthesis creates oxygen.

Mouse in a box

The airtight chamber was built to be a powerful demonstration of how plants act as the lungs of planet Earth, providing all the oxygen that sustains us. It echoes the experiment first tried by the scientist Joseph Priestly in 1772. He showed that a mouse could survive in an airtight chamber full of plants, yet could only live a short time in a box without them. "This time, I was the mouse" said Iain when I caught up with him recently...

"When I went into the chamber they sucked out half the oxygen, so they could look at the effects of oxygen deficiency. It was like being suddenly stuck on the top of a very high mountain. I started to get altitude sickness - headache, everything was incredibly slow, I was trying to do tests... I was overly deliberate and taking ages."

"All I needed to do was rest, try to use less oxygen and make sure those plants kept on photosynthesising - I kept watering them just to be sure!"

"It was funny, but after that, I started to feel much more paternal toward them".

Man in a Box (Eden Project)

Ancient air and a chilli

Iain is as enthusiastic about sharing the secrets hidden in a lump of rock as he is when scaling giant trees or exploring deep caves. One rock in particular that got him really excited was a chunk of iron ore from a freshly blasted cliff in South Africa. Like a geological Nigella Lawson he relishes in the recipe for extracting oxygen from the ore before inhaling the fruits of his labour, air that was created by plant life two and a half billion years ago.

The height of his gastronomic revelations comes when he scoffs a whole chilli, to demonstrate how plants,like spiky cycads, built up resistance to predators - the most terrifying of all (if you're a plant) being the sauropod dinosaurs who he calls the 'ultimate salad predators'. Holding up the remains of the chili Iain says "forget about cycads, THAT could have brought down a 70 tonne sauropod!"

Other highlights making this programme 'not-to-be missed' include a rainforest inside a Vietnamese cave, plants talking to each other, macro-photography of leaf pores breathing, and a climb up the biggest organism on earth - the 85-metre-tall, 1500-year-old Giant sequoia in California. Epic!

When dinosaurs evolved they posed a threat to the plant kingdom. They were the biggest herbivores ever to live on land and many of them travelled in groups, stripping plants of their leaves. In response to herbivory, plants developed defences, the most obvious being thorns and spikes. They then went on to evolve chemical weapons, in the form of foul tasting chemicals and toxins.Chillis contain a chemical called capsaicin, which is essentially a toxin.

I'm watching this beautiful series back-to-back, having recorded it all. I'm loving it - it's very innovative but isn't there an error in it's explanation of photosynthesis in programme one? Iain says that it's a water molecule that's broken apart, releasing the waste product oxygen, leaving the hydrogen that is used for strength and growth of the plant. Surely it's a CO2 molecule that's blasted by the photons of light. carbon and oxygen are then released, the carbon being used for the growth of the plant. Am I right... perhaps not... I'm only a geologist!!!!

The water molecules are split with the hydrogen ion attaching to NADP+, carrying the electrons and energy required for the light-independent reactions, which requires CO2 to make sugar molecules. So yeah, the O2 is a waste product when water is split.

O2 is released as a waste product when H2O is split the hydrogen ions attach to the electron carrier NADP+, becoming NADPH, which carries the free electrons released by the pigments, to take into the light-independent reactions, where CO2 is used to make carbohydrates for the plant

Dear Production Team,First of all, I would like to say that I love this series. I would've never thought that plants and grass could be so interesting. This series really was for me a real eye opener.

Secondly, Is there a possibility that I can buy/download the music used in this series especially the intro song. I've already contacted the website of www.paulleonardmorgan.com, this because Paul leonard-morgen is named in the closing credits of these three episodes.

According to them you "the production team" might be able to help me with the music.

Dear W.van Eijk, Thanks for posting this enquiry - most of the music we use is not, and can not be released for contractual reasons. I will ask the production team about this but it is unlikely that they will be able to provide the music. I do know that some of the music was reused from 'How Earth Made Us' which was composed by Ty Unwin, but the main music was by Paul Leonard-Morgan. Best wishes, Paul